basically, what hpw said.
to flesh it out a bit more...
unlike the way some people use these terms "division of labor," "trade," "capitalism," etc, not all aspects of these concepts can be reduced to what two individuals do with each other.
so to me "division of labor" doesn't mean that two people are good at different things, and take advantage of that, it means that groups of people are assigned tasks as part of an "efficient running of society".
here are sites that back that up:
the second one gets at more of the point, and references marx and engel's input on the topic.
the same principle goes for trade.
ancaps are particularly notorious for attempting to simplify everything that happens in society for interactions between two people. it is perhaps the most significant (or maybe just the most obvious) flaw in their thinking.